🤖 AI Summary
Large language models (LLMs) frequently exhibit tool hallucinations—erroneous tool selection or invocation—during tool-augmented reasoning, undermining reliability and safety. Method: This work formally defines and categorizes tool hallucinations and introduces *reliability alignment*, a novel paradigm that expands the action space with *uncertainty-aware actions* (e.g., deferring invocation or requesting clarification) to enable robust, calibrated decision-making. We construct RelyToolBench, the first hallucination-aware evaluation benchmark, equipped with dedicated metrics, and propose Relign—a unified framework integrating supervised fine-tuning and reinforcement learning for reliability-aligned training. Contribution/Results: Extensive experiments demonstrate that Relign significantly reduces tool hallucination rates, improves task success rates and execution efficiency, and yields more stable, interpretable, and trustworthy LLM-tool interactions across diverse multi-step tool-chain scenarios.
📝 Abstract
Large Language Models (LLMs) have expanded their capabilities beyond language generation to interact with external tools, enabling automation and real-world applications. However, tool hallucinations, where models either select inappropriate tools or misuse them, pose significant challenges, leading to erroneous task execution, increased computational costs, and reduced system reliability. To systematically address this issue, we define and categorize tool hallucinations into two main types, tool selection hallucination and tool usage hallucination. To evaluate and mitigate these issues, we introduce RelyToolBench, which integrates specialized test cases and novel metrics to assess hallucination-aware task success and efficiency. Finally, we propose Relign, a reliability alignment framework that expands the tool-use action space to include indecisive actions, allowing LLMs to defer tool use, seek clarification, or adjust tool selection dynamically. Through extensive experiments, we demonstrate that Relign significantly reduces tool hallucinations, improves task reliability, and enhances the efficiency of LLM tool interactions.